1. Field of the Invention
The present invention relates to an image reading apparatus to read document images and used in copy machine and the like.
2. Description of the Related Art
Conventional image reading apparatuses (hereinafter referred to as "stationary platen panning devices") are known which read the image of an entire document by placing a document on a glass platen at the image reading position of a static reader, and transporting said document over said glass platen at a constant speed. In stationary platen panning devices, a document must be transported onto the glass platen with precision in order to accurately read the document image. To this end, stationary platen panning devices are known to provide a transport roller to transport a document between said transport roller and the glass platen.
In such stationary platen panning devices, although a document can be transported with precision in the range of the nip formed between the glass platen and the transport roller when said document is gripped between the transport roller and the glass platen, a disadvantage arises insofar as the document curls along the transport roller on the upstream side and downstream side of said nip.
On the other hand, stationary platen panning devices typically have a reader with a reading range capable of reading the width of the document in the document transport direction in a single pass. When the stationary platen panning device is an analog copy machine, the single pass reading range of the reader is particularly broad. Accordingly, the nip width between the transport roller and glass platen must be broader than the single pass reading range of the reader. Since the diameter of the transport roller in contact with the glass platen must be increased, therefore, the size of the image reading apparatus is increased.